Generally, this type of hothouses for cultivation are enclosed with transparent films or glass plates for maintaining the inside temperature higher than the outside temperature so that plants can grow even in cold seasons as in winter when outdoor raising is impossible or plants can be raised quickly by forcing culture. However, in the northern hemisphere as in Japan, when plants are cultivated in a plurality of rows which are arranged from south to north, although the plants on the southern side receive the sunlight directly, those on the northern side which are hidden by those on the southern side are shone for shorter period and receive substantially less sunlight In summer, when the angle of elevation of the sun is large and the sunlight is strong, there is practically no problem. On the contrary, in winter when the shining hours are short and the angle of elevation is small, it is difficult to assure sufficient sunshine to the plants on the northern side, thereby the plants on the northern side grow so slower than those on the southern side as to make a delay of harvest-time or even to become sterile because of bad growth. Thus, a hothouse was developped in which the roof surface is inclined toward the southern side and the soil surface is shaped as steps with the northern side higher than the southern side so that the plants on the northern side receive sufficient sunshine. This type of hothouse presents problems because it is difficult or even impossible to construct such a hothouse on a flat horizontal surface although it can be realized relatively easily on a special surface configuration such as on a mountainside. There are apparently many hothouses in which mechanical installations for temperature control are provided. However, this results in an additional expense for such installations as well as great operation and maintenance cost. There are also hothouses in which the roof is covered by a sunshade sheet. However, this type of hothouses are not effective to the maintenance of temperature because the sunshine shade is for protecting the plants from withering against strong sunshine.
The present invention was accomplished in view of avoiding the above-mentioned drawbacks to provide a hothouse composed of transparent enclosing members wherein reflexion plates are provided on the northern side for reflecting the sunlight toward the soil surface inside the hothouse. With this construction, the plants on the northern side are provided with sufficient sunlight.
Another object of the present invention is to provide a hothouse wherein a shutter is provided which can be opened or closed along the transparent roof for preventing the temperature fall in the hothouse by providing a heat insulation air space between the roof and the shutter. The present invention also aims at providing an effective structure of the shutter for the heat insulation structure.
Another object of the present invention is to provide a hothouse comprising drainage for guiding condensed water drops so that they do not fall in the hothouse, the water drops being created on the roof surface, in particular on the lower surface of the shutter when it is closed because the respiration of the plants and the action of the installations for air mixing cause the difference of temperature between the inside high temperature of the hothouse and the outside low temperature.
Another object of the present invention is to provide a hothouse wherein ventilation control can be realized, as a result of considerations on the operation control of the shutter and on the construction of the hothouse as a structure.
Another object of the present invention is to provide a hothouse comprising active mechanical temperature control installations for maintaining appropriately the inside temperature of the hothouse, the installations being mainly composed of an air mixing apparatus which is especially effective when the shutter is closed.
Another object of the present invention is to provide a hothouse comprising, as temperature control installations, a duct work for hot water under the ground for maintaining appropriately the inside temperature of the hothouse, hot water then circulating in the duct work for heating effectively the inside of the hothouse.
A further object of the present invention is to provide a hothouse comprising, as temperature control installations, water sprinklers on the roof for preventing snow to lie or for promoting snow to melt so that the hothouse can be used even in winter.
A further object of the present invention is to provide a hothouse being adapted for each of the objects mentioned above based on further considerations on the details of the structure of the shutter to be used for a hothouse.
A further and not the last object of the present invention is to provide a hothouse comprising an improved flowerpot for cultivation suitable for use in the hothouse.